This invention relates, in general, to the handling of web material and more particularly to the means and method for indicating when the web material remaining on the supply spool has been depleted to a predetermined amount, such as the end portion.
Although the invention is applicable to various web, tape, strand or ribbon-like materials, it has been found particularly useful in the environment of ink ribbons as used in serial printers. Therefore, without limiting the meaning of the word "ribbon", the invention will be described in this environment.
In devices, in which any web material is to be delivered or transferred from a rotatable reel, drum, spool, spindle or a like receptacle to another similar and compatible receptacle, it is normally desirable to provide a means to indicate when the web material is depleted from the supply spool. This is of particular importance in the environment of ink ribbons employed in serial printers, and is even more important in automatic text-editing typewriter applicaitons. Without some indication or control regarding the ribbon supply in an automatic text-editing typewriter, a portion of a page of text could be automatically typed without a supply of ribbon being available in the typewriter.
It has been known to employ various types of physical pins or clips attached to the ribbon near the end of the ribbon supply to either physically move a lever or to provide electrical contact to sense the end of the ribbon supply as disclosed in U.S. Pat. Nos. 314,016, 428,264 and 3,404,628. It is also known to employ rod or lever means, which project through the supply hub upon the depletion of the ribbon on the supply spool to sense the end-of-ribbon point as disclosed in U.S. Pat. Nos. 655,985 and 3,232,229. In U.S. Pat. Nos. 725,919, 2,251,162 and 2,458,339 a follower or lever is employed which contacts the outer periphery of the ribbon material and through its pivotal motion during the depletion of the ribbon, signals the end of the ribbon supply on the spool.
Accordingly, it is a primary object of the instant invention to develop an improved indication of the depletion of web material on a supply spool.
Another object of this invention is to obtain the occurrence of a definite action near the end portion of ribbon on the supply spool, which can be detected and acted upon as desired.
Yet another object of the current invention is to design a simple and reliable means and method for indicating the depletion of web material on a supply spool.
Other objects and advantages of the present invention will be evident from the specification and claims when read in conjunction with the accompanying drawing illustrative of the invention.